Process for in situ retorting of oil shale



Oct. 31, 1967 E. E. BURGH PROCESS FOR IN SITU RETORTING OF OIL SHALE Filed Oct. 24, 1965 INVENTOR ERNEST E BURGH BY United States Patent Ofiice 3,349,848 Patented Oct. 31, 1967 3,349,848 PROCESS FOR EN SITU RETORTING OF OIL SHALE Ernest E. Burgh, 10035 W. 29th, Denver, Colo. 80215 Filed Oct. 24-, 1965, Ser. No. 504,793 16 Claims. (Cl. 16639) This invention relates to the recovery of hydrocarbon from oil shales and more particularly to the preparation of in situ retorts and the retorting of shale therein.

United States Patent 3,001,776 issued to H. K' van Poollen on Sept. 26, 1961, teaches a recovery process wherein vertical retorts, terminating in cross drifts, are formed in oil shale. Shale in the retort is ignited and a combustion wave is passed through the retort to release hydrocarbons from the shale. The released oil gravitates downwardly and is collected via the cross drifts.

The Van Poollen process does not deal with the problem faced when a formation contains kerogen-lean or kerogen-rich strata which differ considerably from the norm of the formation. The present invention provides the solution to this problem and also provides a relatively inexpensive means of forming in situ retorts.

Described briefly in terms of one retort, the process of this invention comprises drilling a pilot hole termimating in cross drifts through an oil shale section, enlarging the pilot hole laterally to form a retort while displacing material removed during the enlargement downwardly into the cross drift, blending leaner kerogen shale with kerogen richer shale or other fuel, returning blended shale to the retort and passing a combustion wave through the returned shale to retort hydrocarbons from the blended shale in the retort and the shale adjacent the retort.

The invention is more fully described by reference to the attached cutaway drawings which depict portions of three rows of retorts in a formation.

The process is carried out in an oil shale bed 1 located between strata 2 and 3 which contain no hydrocarbonbearing marl. Initially, a number of pilot holes 4 are drilled into the formation at intervals of about 75 to about 150 feet. Cross drifts 5 are drilled to connect pilot holes 4 at the top of shale bed 1. Cross drifts 6 are driven to connect pilot holes 4 at the bottom of shale bed 1. Remotely controlled bulldozers 7 are utilized to fracture and break up the shale adjacent pilot holes 4 so as to form enlarged retorts 8. The fractured broken shale 9 is dozed into pilot holes 4 and falls onto conveyers 10 which carry the shale toward storage pit 11. One conveyer 10 is provided for each retort being excavated. Movable conveyers 12, in pit 11, direct shale 9 to the correct storage pile.

The marl in bed 1 is classified according to its fuel content for purposes of illustration in three categories; i.e., lean, average, and rich; by examination of cuttings at intervals during the drilling of pilot holes 4. Conveyers 12 are positioned, from time to time in accordance with the determined fuel content of the fractured shale, to deliver shale 9 received from conveyers 10 to lean storage pile 13, average storage pile 14, or rich storage pile 15.

The shale can also be sized. A preferred size is 24 inches though smaller and much larger particles can be used. If the shale fracturing device does not furnish shale particles of desired size, the larger particles can be reduced in size by conventional means, for example, by crushing.

Screw conveyors 16 then direct desired amounts of shale 9 from piles 13, 14, and to mixer 17. Mixed marl 19 is then elevated through shaft 20, by screw conveyer 21, to drifts 5 where conveyers 22 direct the mixed marl 19 into excavated, partially filled retort 23. The

marl is held in retort 23- by any suitable retaining.

means 24.

The mixed marl 19 dumped into retort 23 is blended so as to be sufficiently hydrocarbon rich to provide heat, through partial combustion, suflicient to educe oil from the shale in an adjacent retort 23, The hydrocarbon content i.e., fuel richness-of the mixture of marl or of marl and a fuel deposited in retort 23 varies with the fuel richness of the shale adjacent the retort and the distance between retorts. Thus, the fuel content of marl 19 adjacent a hydrocarbon-lean streak in bed 1 will be higher than that of the lean shale. Other fuel-for example, coal, coke or petroleum residuum-may be added to even a rich marl if the area adjacent the retort from which hydrocarbons are to be educed is great and the kerogen content of the shale is high.

After a retort is filled and sealed by conventional means, an oxidant, preferably air, is introduced into the retort and the marl ignited, at one end or the other, by conventional means. Either cocurrent or countercurrent combustion techniques can be utilized to retort the oil shale, but countercurrent combustion is preferred because the heat is maintained behind the combustion zone and because the combustion front can be reversed to provide additional heat if needed.

Countercurrent combustion, generally conducted at temperatures in the range of about 700-1500 F., is depicted as progressing in retort 25. Air is introduced into retort 25 via drift 26, passes downwardly through marl 19 in retort 25 to combustion zone 27 which is passing upwardly through retort 25. Combustion gases then pass downwardly and are exhausted, along with kerogen vapors and liquids, through downwardly sloping drift 6 and thence removed to the surface through shaft 20. The rate of combustion front movement and combustion zone temperatures are increased by increasing the amount of oxidant contacting the combustion zone.

on completion of excavation in a row of retorts, the cross drifts necessary for the next row are drilled and the equipment moved to the new location. The shale beds between the retorts can be fractured if desired.

While the process of this invention has been described both generally and specifically, various facets of the process and equipment will now be dis-cussed in further detail.

Pilot holes 4- need be only about 3-12, and preferably 8, feet across. These holes are enlarged to diameters as large as about -80 feet by bulldozers which begin operations from cross drifts 5. Practically then, the cross drift width will be greater than the bore hole diameter. Bulldozers can be utilized in this operation as low shear is required to break up the marl when applied perpendicular to the depositional plane.

Remotely controlled bulldozers are depicted as breaking up the shale adjacent pilot holes 4. However, humanoperated dozers can also be used. A number of dozers can be utilized to efiiciently displace marl into pilot holes 4. Other variations on the above-described process exist. For example, hydraulic mining can be used in the process of this invention. Alternately, ripping teeth attached to a dozer can break up the marl which is then bladed into the pilot hole.

The broken shale 9 is depicted as falling onto belt conveyer 10 from whence it is deposited on an appropriate storage pile by belt conveyer 12. In an alternate procedure, the lower end of pilot holes 4 can be fixed with a hopper having a directional outlet. In this embodiment of the invention, multiple conveyer belts would be laid the entire length of drifts 6 and would be directed, at

3. the exit end, to an appropriate storage pile. The hopper outlet would be directed from belt to belt as the kerogen content of the shale varied, thereby separating the broken shale 9 into fractions of desired kerogen content.

Additionally, screw conveyers are depicted as being used in the storage pit area and to lift the mixed marl 19 vertically. Other types of conveyers can be utilized in these situations with equal facility. Thus, a bucket conveyer can be readily substituted for screw conveyer 21.

It is intended that these and other embodiments of my invention obvious to those skilled in the art be in cluded with the scope of my invention as claimed.

Now having described my invention, what 1 claim is:

1. In a process for recovering hydrocarbons by the partial in situ combustion of oil shale wherein a hole is drilled into an oil shale section from which hydrocarbon is to be recovered, the hole is enlarged to form a retort in said oil shale section, and a combustion front is passed through shale in said retort, the steps comprismg:

(a) fracturing oil shale adjacent the said hole to enlarge the said hole to a retort and to form fractured particulate shale,

(-b) displacing the through said hole,

(c) classifying the particulate shale according to the fuel content of said particulate shale,

(d) blending at least one material of relatively higher fuel content with a relatively hydrocarbon-lean fraction of said particulate shale to form a shale mixture having a fuel content greater than that of said lean fraction, and

(e) passing a combustion front through said shale mixture to educe fluid hydrocarbon from said shale mixture.

2. The process of claim 1 wherein the combustion front is maintained at temperatures of from about 700 to about 1500 F.

3. The process of claim 1 wherein the oil shale adjacent the retort is fractured prior to passing a combustion front through the shale mass in the retort.

4. The process of claim 1 wherein the oil shale adjacent the said hole is hydraulically mined.

5. The process of claim 1 wherein a relatively hydrocarbon-rich particulate shale is mixed with said relatively hydrocarbon-lean fraction.

6. The process of claim 1 wherein said at least one materialv of relatively higher fuel content is a hydrocarbon.

7. In a process for the in situ retorting of oil shale by passing a combustion front through fractured shale in a retort wherein pilot holes are drilled through an oil shale bed, the pilot holesare enlarged by fracturing the shale to form a retort, and the fractured shale is retorted, the steps comprising:

(a) incrementally fracturing the shale surrounding the pilot hole,

(b) displacing the fractured shale downwardly through the said pilot hole,

(c) classifying the shale into fractions of predetermined kerogen content,

(d) mixing fractions of the classified fractured shale,

(e) introducing the mixture of fractured shale into an excavated retort, and

(f) conducting in situ combustion in the fractured shale at temperatures of about 700 to about 1500 F.

8. The process of claim 7 wherein the kerogen content of mixtures of fractured shale introduced into the excavated retort is sufiicient to free hydrocarbons from the formation adjacent the retort on in situ combustion of the mixtures of shale in the retort.

9. The processing of claim 7 wherein the shale is fractured by ripping, scraping and/ or gouging.

10. In a process for the in situ retorting of oil shale particulate shale downwardly 4: by partial combustion wherein pilot holes are drilled into an oil shale bed, the pilot holes are enlarged by fracturing the shale aurrounding the pilot hole to form retorts and the fractured shale retorted, the steps comprising:

(a) incrementally fracturing from top to bottom the shale surrounding the pilot hole to form a retort,

(b) displacing the fractured shale downwardly through said pilot hole, and

(c) introducing fractured shale into the formed retort prior to conducting in situ combustion in the introduced shale.

11. The process of claim 10 wherein fuel is disseminated in the fractured shale prior to conducting in situ combustion in the introduced shale.

12. The process of claim 10 wherein the fuel content of the fractured shale in the excavated retort and the rate of introducing oxidant into the retort are suflicient to provide a combustion from temperature of from about 700 to about 1500 F. and to produce substantially sufficient heat by combustion of the fractured shale in the retort to educe hydrocarbons a substantial distance from the retort in the oil shale bed.

13. The process of claim 10 wherein the fracturing is by ripping, scraping and/ or gouging.

14. The process of claim 10 wherein the fracturing is by hydraulic mining.

15. The process of claim 10 wherein kerogen-rich shale is blended with kerogen-lean shale prior to introducing fractured shale into the excavated retort.

16. In a process for recovering hydrocarbons by the partial in situ combustion of oil shale wherein a hole is drilled into an oil shale section from which hydrocarbon is to be recovered, the hole is enlarged to form a retort in said oil shale section, and a combustion front is passed through the shale in said retort, the steps comprising:

(a) fracturing oil shale adjacent the hole to enlarge the hole to a retort and to form fractured particulate shale,

(b) displacing the through said hole,

(c) classifying the particulate shale according to the fuel content of said particulate shale,

(d) blending at least one material of relatively higher fuel content with a relatively hydrocarbon-lean fraction of said particulate shale to form a shale mass having a fuel content greater than that of said lean fraction,

(e) fixing an openwork particulate shale-retaining means across the lower opening into said retort,

(f) introducing classified shale into said retort to fill said retort with said shale mass,

(g) introducing into said shale mass an oxidant in amounts sufiicient to support a combustion zone in said shale mass,

(h) igniting said shale mass at one end of said retort,

and

(i) recovering educed hydrocarbon.

particulate shale downwardly References Cited UNITED STATES PATENTS 1,856,836 5/1932 Howell 299-2 X 1,913,395 6/1933 Kerrick 299-2 2,481,051 9/1949 Uren 299-2 3,001,776 9/1961 Van Poollen 299-2 3,034,773 5/1962 Legatski 299-2 X 3,223,158 12/1965 Baker 166-40 X 3,228,468 1/1966 Nichols 16640 X 3,303,881 2 /1967 Dixon 166-39 X CHARLES E. OCONNELL, Primary Examiner.

STEPHEN I. NOVOSAD, Examiner. 

10. IN A PROCESS FOR THE IN SITU RETORTING OF OIL SHALE BY PARTIAL COMBUSTION WHEREIN PILOT HOLES ARE DRILLED INTO AN OIL SHALE BED, THE PILOT HOLES ARE ENLARGED BY FRACTURING THE SHALE AURROUNDING THE PILOT HOLE TO FORM RETORTS AND THE FRACTURED SHALE RETORTED, THE STEPS COMPRISING: (A) INCREMENTALLY FRACTURING FROM TOP TO BOTTOM THE SHALE SURROUNDING THE PILOT HOLE TO FORM A RETORT, (B) DISPLACING THE FRACTURED SHALE DOWNWARDLY THROUGH SAID PILOT HOLE, AND (C) INTRODUCING FRACTURED SHALE INTO THE FORMED RETORT PRIOR TO CONDUCTING IN SITU COMBUSTION IN THE INTRODUCED SHALE. 